Sublimation vacuum pump having a removable gas permeable condenser

ABSTRACT

A sublimation type vacuum pump includes a gas permeable condensing structure surrounding the source of getter material to be sublimed. The condensing structure is affixed to a flange assembly for sealing the getter and condensing structure within an evacuable envelope to be pumped. Fluid coolant conduits pass through the flange and into heat exchanging relation with the condensing structure for cooling the condenser and flange. In one embodiment the side wall of the condensing structure includes a plurality of telescoped cylinders and in a second embodiment the side walls of the condensing structure includes a circular array of condensing louvers.

United States Patent [1 1 [111 ,924,

Harra Dec. 9, 1975 SUBLll/IATION VACUUM PUMP HAVING A Primary ExaminerWilliam L. Freeh REMOVABLE GAS PERMEABLE Assistant ExaminerG. P. LaPointe CONDENSER Attorney, Agent, or Firm-Stanley Z. Cole; Leon F. 75 Inventor: David J. Harra, Palo Alto, Calif. Herbert [73] Assignee: Varian Associates, Palo Alto, Calif. [57] ABSTRACT Filed; 1974 A sublimation type vacuum pump includes a g s per- [21] APPL No; 453,739 meable condensing structure surrounding the source of getter material to be sublimed. The condensing structure is afiixed to a flange assembly for sealing the [52] U.S. Cl. 417/51 getter and condensing tructure within an evacuable [51] Int. Cl. F0413 37/02 envelope to be pumped. Fluid Coolant conduits pass [58] Field Of Search 417/48, 49, 51 through the flange and into heat exchanging relation with the condensing structure for cooling the con- References Cited denser and flange. In one embodiment the side wall of UNITED STATES PATENTS the condensing structure includes a plurality of tele- 3,140,s20 7/1964 Clausing 417/51 scoped Cylinders and in a Second embodiment the Side walls of the condensing structure includes a circular array of condensing louvers.

3,207,423 9/1965 Huber et al....

3,211,361 10/1965 Flinn 3,442,139 5/1969 Munro.... 417/48 16 Claims, 10 Drawing Figures lml' F /6 l 1 l O [I II 1' 1 0 l3 l4 l2 5 77- E L l5 2 41 f 5 25 T hi 1* n 2% Patent Dec. 9, 1975 Sheet 1 of 3 US. Patent Dec. 9, 1975 Sheen 2 of3 3,924,967

LO no as m I ll m GE US. Patent Dec. 9, 1975 Sheet 3 of3 3,924,967

SUBLIMATION VACUUM PUMP HAVING A REMOVABLE GAS PERMEABLE CONDENSER BACKGROUND OF THE INVENTION The present invention relates in general to sublimation vacuum pumps and more particularly to an improved sublimation vacuum pump including a gas permeable getter condensing structure formed and arranged as an integral unit with a demountable sealing flange for sealing the condensing structure to an evacuable envelope to be pumped.

DESCRIPTION OF THE PRIOR ART Heretofore, sublimation getter pumps have been proposed wherein a source of getter material was surrounded by a condensing structure carried from a sealing flange as an integral unit for sealing the condensing structure within an evacuable envelope to be pumped. However, in these prior pumps, the condensing structure had openings therein for providing gas communication passageways between the interior of the condensing structure and its surrounds within the evacuable chamber to permit flow of gas to be pumped from the chamber to be evacuated into the condensing structure. The condensing structure and the gas passageways therein were so arranged that a substantial amount of the sublimed getter material could pass out of the condensing structure in line-of-sight trajectories through the gas communication passageways and onto the interior surfaces of the structure to be evacuated.

In many cases this prior structure resulted in condensation of getter material and, thus, the gettering of gases on surfaces which were not cooled in use. These uncooled accumulations of getter material resulted in undesired out-gassing within the system. Furthermore, such accumulations of getter material were obtained in regions of the evacuable structure which were difficult to clean. As a consequence, the getter material would build up and flake off in relatively large flakes which could short certain of the electrical elements within the pump or pumped chamber. Once pealing has commenced, the extremities of the flakes are no longer cooled sufficiently in the presence of the sublimation heat load and as a consequence undesired out-gassing occurs. In some cases, the flakes could come to rest upon elements at elevated temperature resulting in undesired out-gassing.

Therefore, there is need, in a sublimation pump, of a condensing structure which is removable as a unit for ease of cleaning and which is formed and arranged so as to condense or collect substantially all, i.e., at least 95percent of the sublimed getter material passing outwardly of the sublimation element along line-of-sight trajectories. At the same time the condensing structure should form a relatively gas permeable structure so as not to unreasonably impede the intrinsic pumping speed of the sublimation pump.

SUMMARY OF THE PRESENT INVENTION The principal object of the present invention is the provision of an improved sublimation vacuum pump of the type having a gas permeable readily removable condenser.

In one feature of the present invention, a source of getter material to be sublimed is surrounded by a gas permeable condenser structure formed and arranged for condensing at least 95 percent of the rays of getter material radiating outwardly in a line-of-sight trajectory from the sublimation source, and such condensing structure including a flange as a unitary part thereof to facilitate rapid removal, cleaning, and replacement thereof, in use.

In another feature of the present invention, fluid cooling conduits are arranged in heat exchanging relation with the condensing surfaces of the condensing structure for cooling same in use.

In another feature of the present invention, the condensing structure includes a plurality of telescoped, radially spaced, cylindrical side wall portions for condensing getter material thereon, and for providing a gas passageway in between the telescoped cylindrical sections.

In another feature of the present invention, the condensing structure includes a circular array of condensing louvers, such louvers being turned relative to a central source so as to intercept substantially all of the rays of getter material radiating outwardly from the source of getter material along line-of-sight trajectories.

In another feature of the present invention, the condensing structure is closed on its inner end by means of a transverse member having an aperture therein to receive a second source of getter material passable axially therethrough into the central region of the condensing structure, whereby a plurality of sublimation sources may be disposed within a common condensing structure.

Other features and advantages of the present invention will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view partly in elevation and partly broken away of a sublimation type vacuum pump incorporating features of the present inventlon,

FIG. 2 is an enlarged detail sectional view of a portion of the structure of FIG. 1 taken along the line 22 in the direction of the arrows,

FIG. 3 is an enlarged detail sectional view of a portion of the structure of FIG. 1 taken along line 3-3 in the direction of the arrows.

FIG. 4 is-an enlarged detail sectional view of a portion of the structure of FIG. 1 taken along line 44 in the direction of the arrows,

FIG. 5 is a side view of a flanged getter condensing structure incorporating alternative features of the present invention,

FIG. 6 is an end view of the structure of FIG. 5 taken along line 6-6 in the direction of the arrows,

FIG. 7 is a sectional view of the structure of FIG. 5 taken along line 77 in the direction of the arrows,

FIG. 8 is an enlarged fragmentary side view of a portion of the structure of FIG. 7 taken along line 8-8 in the direction of the arrows,

FIG. 9 is a sectional view of the structure of FIG. 8 taken along line 9-9 in the direction of the arrows, and

FIG. 10 is an end view of the structure of FIG. 5 taken along line 10-40 in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 there is shown a sublimation vacuum pump 1 incorporating features of the present invention. Pump 1 includes an evacuable chamber 2, as of stainless steel, having a lower rectangular portion 3 connected to an upper cylindrical portion 4 via the intermediary of a centrally apertured end plate 5. A flange 6 is fixedly secured, in a gas tight manner to the upper end of the cylindrical portion 4 for mating with a flanged chamber to be evacuated.

A valve 7 is mounted within a central aperture 8 of the flange 6 for controlling the flow of gas between the vacuum pump 2 and the structure to be evacuated. The valve 7 includes an actuator rod 9 pivotally connected toa horizontally movable actuating plunger 11 via the intermediary of a pivotable plate 12. Plate 12 is pivotably supported from the inside wall of the cylindrical chamber 4 via mounting bracket 13 and plate 12 is pivotably mounted to the bracket 13 via pivot pin 14. A suitable bellows, not shown, provides a gas tight seal between the horizontally movable actuator 11 and the inside wall of the chamber 4.

A sublimation pump structure 15 is disposed within the lower rectangular chamber 3 of the pump 2. The sublimation pump 15 includes first and second telescoped cylindrical condensing members 16 and 17. The first cylindrical condensing member 16 is fixedly secured to a demountable flange 10 via brackets 18 disposed at intervals around the periphery of the cylindrical condensing member 16. Similarly, the second cylindrical condensing member 17 is mounted to the end of the first cylindrical condensing member 16 via the intermediary of a plurality of brackets 19. An end closing plate 21 is fixedly secured to and carried from the inner end of the second cylindrical condensing member 17 via the intermediary of a plurality of brackets 22.

The condensing cylinders 16 and 17 as well as the end closing plate 21 are hollow to provide fluid coolant passageways therethrough for cooling of the condensing structure in use. In a typical example, the cooling fluid is room temperature water which is fed through the condensing structure in sufficient quantity to cool the condensing structure in use to a temperature below 75C and preferably below 50C. Fluid coolant is fed through the flange 10 via input conduit 24 which is connected in fluid communication with an interior cylindrical annulus 25 of the first condensing cylinder 16 and thence via a stainless steel pipe 26 interconnecting the inner end of the first cylindrical member 16 with the adjacent end of the annular chamber 27 in the second condensing cylinder 17. Thence, the fluid coolant is conducted via a pipe 28 into a hollow colling chamber 29 of the end plate 21. Fluid coolant is then returned from the end plate chamber 29 via pipe 31 including take apart flanged connector 32 to a hollow annular chamber 33 in the flange 10 for cooling of the flange. The coolant is exhausted from the flange 10 via exhaust 34.

Coolant pipe 26 which interconnects the first and second condensing cylinders 16 and 17 is formed into a semicircular shape to hug the outer cylindrical surface of the second condensing cylinder 17 and also contains a take apart flange. The source 35 of getter material is disposed generally on the axis of the condensing structure and is supported from the flange 10 via a support tube 36 serving as one conductor of a two wire lead for feeding electrical heating current to an electrical heating element disposed within the hollow interior of the getter source 35. Source 35 is supported from the tube 36 via the intermediary of a plurality of thin support legs 37 which provide high impedance thermal paths to 4 inhibit the conduction of heat away from the source 35. The support tube 36 is secured to the flange 10 by means of an auxiliary flange 38 to facilitate replacement of the getter source 35.

The first and second cylindrical condensing members 16 and 17 are telescoped at their adjacent ends by an amount sufficient to eliminate the possibility of a lineof-sight path from the source 35 to the surrounds of the condensing structure 15 via the intermediary of the annular gas passageway 39 defined by the radial gap between the outside of the second condensing member 17 and the inside of the first condensing member 16. Also the end plate 21 is spaced from the end ofthe second cylindrical condensing member 17 and overhangs the outer periphery of the second condensing cylinder 17 by an amount to prevent a line-of-sight path from the getter source 35 to the surrounds of the condensing structure 15 via the annular gas passageway 41 defined between the adjacent end of the condensing cylinder 17 and the end cover plate 21.

The advantage of the sublimation vacuum pump of FIG. 1 is that substantially all, i.e., essentially percent of the getter material that is radiated away from the source 35, in line-of-sight trajectories, is collected upon a cooled surface of the condensing structure 15 which includes not only the cylindrical side condensing structures 16 and 17 but the end cover plate 21 and the flange 10. In this manner, condensation of substantial amounts of getter material in regions that cannot be readily cleaned is avoided in use. Also, condensation of getter material on surfaces that are not cooled is prevented, thereby avoiding undesired out-gassing of gases gettered on such surfaces. A further advantage to the sublimation pump in FIG. 1 is that all of the condensing surfaces can be readily cleaned by disconnecting the flange 10 and removing the condensing structure as a unit and immersing the unit in a suitable acid etchant for removing the condensed getter material. In this regard all of the metallic elements of the sublimation pump, particularly the condensing structures, are made of stainless steel.

In a typical example the flange 17 is 18 inches in outside diameter, first cylinder 16 is approximately 15 inches in outside diameter and the second cylinder 17 is 11 inches in outside diameter and the overall axial length of the condensing structure 15 is 18 inches. The annular chambers 25 and 27 within the condensing cylinders 16 and 17 are 0.37 inch thick. This pump has an intrinsic pumping speed for nitrogen of 20,000 liters per second within sublimation pump structure 15 and a net pumping speed for nitrogen of 6,000 liters per second outside structure 15 within housing 3.

Referring now to FIGS. 5-10 there is shown a second sublimation pump incorporating alternative embodiments of the present invention. More particularly, the condensing structure 45 comprises a circular array of liquid cooled getter condensing louvers 46. The louvers 46 are axially directed of the condensing structure. The louvers are fixedly secured to a demountable flange 47 to be mounted to the housing 3 to be evacuated. Each of the louvers includes an input tubulation 48 and an output tubulation 49 coupled in fluid communication with cooling conduit portions 51 and 52, respectively formed in the individual louvers 46. The input and output fluid coolant passageways 51 and 52 are interconnected at the inner ends of the louvers 46 via the intermediary of a transverse passageway 53 formed by a folded over tab portion 54 of the louver. In a typical exwill cool the condensing structure to less than 75C "while utilizing titanium sources 35 and 35 simultaa channel 56 is formed on the outer wall of the flange 47 and connected in series with the coolant flow neously at 1500 watts dissipation. The coolant employed is water at ambient roomtemperature operating with a flow rate of a few gallons per minute at 20 psi A pressure drop. All of the elements of the condensing structure 45 are made of stainless steel to facilitate cleaning by etching.

Although, as thus far described, the inner ends of the condensingstructures l and 45, respectively, have been formedby plates, this is not a requirement. In case greater net pumping speed is desired the inner ends of through the louvers for cooling of the flange 47 in use.

As in the embodiment of FIG. 1, the getter sublimation source 35 is supported from the flange 47 by means of an axially directed tubular support structure 36 which is fixedly secured to the flange at one end and serves to support the getter source 35 centrally of the louvered condensing structure 45.

The inner end of the louvered condensing structure 45 is closed off by a circular end plate 57 which is fixedly secured to a ring 58 carried at the inner end of the louvers 46. End plate 57 has a pair of coaxially disposed generally rectangular coolant channels 59 and 60 formed thereon in heat exchanging relation with the cover plate 57 for cooling thereof in use. Coolant is conducted from the supporting flange 47 to the end closing plate 57 via the intermediary of an axially directed conduit 61 which connects into a flanged coupling structure 62 and thence into the outer channel.

58. Coolant flows through the outer channel 60 to the inner channel 59 via radially directed channel portion 63 and thence from the end of the inner channel 59 to a second flanged coupler 64 via a pipe 65. Flanged coupler 64 is connected to an axially directed pipe 66 for conducting the fluid back to the flange 47 and thence into the circular array of louvers 46. Thus, coolant is fed into the flange 47 via input tubulation 67 through the coolant passageways of the condensing structure and back out of the flange 47 via output tubulation 68.

The sublimation condensing structure 45, as in the embodiment of FIG. 1, is mountable and demountable as a unitary structure via flange 47 to facilitate cleaning, as by etching. A central aperture 71 is provided in the end closing plate 57 to accomodate passage therethrough of a second getter support tube 36 and getter source 35' which projects through the aperture 71 into a central region of the condensing structure 45 from the other end thereof.

The condensing structure 45 has the louvers 46 arranged so as to prevent any line-of-sight path from either of the getter sources 35 and 35' to the surrounds of the condensing structure 45 other than through an annular space between the central aperture 71 in the end plate and the stem 36 of the second getter structure. More particularly, in the structure of FIGS. 5-10, less than 2 percent of the line-of-sight trajectories from either of the sources 35 passes out through aperture 71.

the condensing structures 15 and 45 are provided with gas passageways therethrough which are arranged to block line-of-sight trajectories from the getter source 35. More particularly, such inner ends may comprise louvers of the type shown for the side walls of condensing-structure 45, or an axially spaced arrangement of a washer and an end closing disk.

What is claimed is:

1. In a sublimation vacuum pump of the type wherein a getter material is sublimed onto a surrounding gas permeable cooled condensing structure for gettering gas from within the evacuable structure coupled in gas communication with said condenser, said sublimation pump including:

condenser means for surrounding a source of getter material which is to be sublimed in use, said condenser means having apertures therethrough arranged so that getter material emanating from the source of getter material will not have line-of-sight passage through said apertures to the outside of said condenser means, said apertures forming passageways for providing gas communication between the outside of said condenser means and the interior surfaces of said condenser means which face the source of sublimed getter material and which are to collect the sublimed material;

flange means coupled to said condenser means so as to form a unitary removable structure for sealing, in a gas tight manner, said condenser means to the evacuable structure to be pumped with said condenser means being disposed within the evacuable structure;

fluid cooling means for directing a stream of cooling fluid inheat exchanging relation with the getter condensing surfaces of said condenser means for cooling same in use; and

all portions of said condenser means which are in the path of line-of-sight trajectories from the source of getter material are carried by said flange means and removable therewith.

2. The apparatus of claim 1 wherein, said flange means is a portion of said condenser means, and wherein said fluid cooling means is coupled in heat exchanging relation to said flange means for cooling said flange means.

3. The apparatus of claim 1 wherein, said condenser means is generally cylindrical in shape having an arcuate side wall portionsurrounding the source of getter material and an inner end wall portion axially spaced from said flange means and from the source of getter material, and wherein said fluid cooling means includes fluid coolant conduit incorporated with both of said side and inner end wall portions.

4. The apparatus of claim 3 wherein, said fluid coolant conduit for said side and inner end wall portions passes through said flange means.

5. The apparatus of claim 4 wherein, said condenser means is dimensioned and arranged for intercepting at least 95 percent of the rays of getter material radiating outwardly in line-of-sight trajectories from the source of getter material.

6. The apparatus of claim 3 wherein, said side wall portion of said condenser means includes a circular array of circumferentially spaced, axially directed louvers, and wherein said circumferential spacing forms said apertures.

7. The apparatus of claim 6 wherein, said inner portion of said condenser means includes a plate affixed across the inner end of said circular array of louvers.

8. The apparatus of claim 7 wherein, said inner end plate has an aperture therein to receive a second source of getter material passable axially therethrough.

9. The apparatus of claim 3 wherein, said side wall portion includes a plurality of generally coaxially arranged cylindrical portions disposed in radially spaced apart and at least partially axially telescoped relation.

10. The apparatus of claim 9 wherein, said inner end portion of said condenser means includes a plate affixed across the inner end of said side wall portion.

11. In a sublimation vacuum pump of the type wherein a getter material is sublimed onto a surrounding gas permeable cooled condensing structure for gettering gas from within an evacuable structure coupled in gas communication with said condenser, said sublimation pump including:

condenser means for surrounding a source of getter material which is to be sublimed in use, said condenser means having gas passageways therethrough for providing gas communication between the outside of said condenser means and the interior surfaces of said condenser means which face the source of sublimed getter material and which are to collect the sublimed material;

flange means coupled to said condenser means so as to form a unitary removable structure for sealing, in a gas tight manner, said condenser means to the 8 evacuable structure to be pumped with said condenser means being disposed within the evacuable structure;

fluid cooling means for directing a stream of cooling fluid in heat exchanging relation with the getter condensing surfaces of said condenser means for cooling same in use;

wherein said condenser means is generally cylindrical in shape having a side wall portion surrounding the source of getter material and an inner end wall portion axially spaced from said flange means and from the source of getter material, and wherein said fluid cooling means includes fluid coolant conduit incorporated with both of said side and inner end wall portions; and

all portions of said condenser means which are in the path of line-of-sight trajectories from the source of getter material are carried by said flange means and removable therewith.

12. The apparatus of claim 11 wherein, said side wall portion of said condenser means includes a circular array of circumferentially spaced, axially directed louvers, and wherein said circumferential spacing forms said circumferential spacing forms said passageways.

13. The apparatus of claim 12 wherein, said inner portion of said condenser means includes a plate affixed across the inner end of said circular array of louvers.

14. The apparatus of claim 13 wherein, said inner end plate has an aperture therein to receive a second source of getter material passable axially therethrough.

15. The apparatus of claim 11 wherein, said side wall portion includes a plurality of generally coaxially arranged cylindrical portions disposed in radially spaced apart and at least partially axially telescoped relation.

16. The apparatus of claim 15 wherein, said inner end portion of said condenser means includes a plate affixed across the inner end of said side wall portion.

Ei TTTTETT STATES PATENT AND TRAUEHLHXRK {JFFKTE (TERTIFECATE OF CGRBIW'EEON PATENT NO. 3, 924,967 DATtD December 9, 1975 ENVENTORB) David J. Harra it is ertified tha? ezror appears in the above-dentified patent and that said Letters Patent a r: area-2! :xmrccted as shown below- Signed and Scaled this thirtieth D f March 1976 [SEAL] Arrest:

RUTH C. MASON Atlesling Officer C MARSHALL DANN (mnmissiunvr of Parents and Trademarks U EJFTED STATES PATENT AND TRAUEMATRK OTFFIGE;

{TERTIFEQATE 0F CGRREETEUN PATENT NO. 3,924,967 DATED December 9, 1975 INVENTOHS) David J. Harra it iscertified tha? error ZIDQE'QFS in the above-identified patent and that said Letters Patent air: awaited 212 shown below:

Column 8, line 25, delete "said circumferential spacing forms".

Signed and Sealed thisthirtieth D a); of March 19 76 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parents and Trademarks 

1. In a sublimation vacuum pump of the type wherein a getter material is sublimed onto a surrounding gas permeable cooled condensing structure for gettering gas from within the evacuable structure coupled in gas communication with said condenser, said sublimation pump including: condenser means for surrounding a source of getter material which is to be sublimed in use, said condenser means having apertures therethrough arranged so that getter material emanating from the source of getter material will not have line-of-sight passage through said aperturEs to the outside of said condenser means, said apertures forming passageways for providing gas communication between the outside of said condenser means and the interior surfaces of said condenser means which face the source of sublimed getter material and which are to collect the sublimed material; flange means coupled to said condenser means so as to form a unitary removable structure for sealing, in a gas tight manner, said condenser means to the evacuable structure to be pumped with said condenser means being disposed within the evacuable structure; fluid cooling means for directing a stream of cooling fluid in heat exchanging relation with the getter condensing surfaces of said condenser means for cooling same in use; and all portions of said condenser means which are in the path of line-of-sight trajectories from the source of getter material are carried by said flange means and removable therewith.
 2. The apparatus of claim 1 wherein, said flange means is a portion of said condenser means, and wherein said fluid cooling means is coupled in heat exchanging relation to said flange means for cooling said flange means.
 3. The apparatus of claim 1 wherein, said condenser means is generally cylindrical in shape having an arcuate side wall portion surrounding the source of getter material and an inner end wall portion axially spaced from said flange means and from the source of getter material, and wherein said fluid cooling means includes fluid coolant conduit incorporated with both of said side and inner end wall portions.
 4. The apparatus of claim 3 wherein, said fluid coolant conduit for said side and inner end wall portions passes through said flange means.
 5. The apparatus of claim 4 wherein, said condenser means is dimensioned and arranged for intercepting at least 95 percent of the rays of getter material radiating outwardly in line-of-sight trajectories from the source of getter material.
 6. The apparatus of claim 3 wherein, said side wall portion of said condenser means includes a circular array of circumferentially spaced, axially directed louvers, and wherein said circumferential spacing forms said apertures.
 7. The apparatus of claim 6 wherein, said inner portion of said condenser means includes a plate affixed across the inner end of said circular array of louvers.
 8. The apparatus of claim 7 wherein, said inner end plate has an aperture therein to receive a second source of getter material passable axially therethrough.
 9. The apparatus of claim 3 wherein, said side wall portion includes a plurality of generally coaxially arranged cylindrical portions disposed in radially spaced apart and at least partially axially telescoped relation.
 10. The apparatus of claim 9 wherein, said inner end portion of said condenser means includes a plate affixed across the inner end of said side wall portion.
 11. In a sublimation vacuum pump of the type wherein a getter material is sublimed onto a surrounding gas permeable cooled condensing structure for gettering gas from within an evacuable structure coupled in gas communication with said condenser, said sublimation pump including: condenser means for surrounding a source of getter material which is to be sublimed in use, said condenser means having gas passageways therethrough for providing gas communication between the outside of said condenser means and the interior surfaces of said condenser means which face the source of sublimed getter material and which are to collect the sublimed material; flange means coupled to said condenser means so as to form a unitary removable structure for sealing, in a gas tight manner, said condenser means to the evacuable structure to be pumped with said condenser means being disposed within the evacuable structure; fluid cooling means for directing a stream of cooling fluid in heat exchanging relation with the getter condensing surfaces of said condenser means for cooling same in use; wherein said condenser means is genErally cylindrical in shape having a side wall portion surrounding the source of getter material and an inner end wall portion axially spaced from said flange means and from the source of getter material, and wherein said fluid cooling means includes fluid coolant conduit incorporated with both of said side and inner end wall portions; and all portions of said condenser means which are in the path of line-of-sight trajectories from the source of getter material are carried by said flange means and removable therewith.
 12. The apparatus of claim 11 wherein, said side wall portion of said condenser means includes a circular array of circumferentially spaced, axially directed louvers, and wherein said circumferential spacing forms said circumferential spacing forms said passageways.
 13. The apparatus of claim 12 wherein, said inner portion of said condenser means includes a plate affixed across the inner end of said circular array of louvers.
 14. The apparatus of claim 13 wherein, said inner end plate has an aperture therein to receive a second source of getter material passable axially therethrough.
 15. The apparatus of claim 11 wherein, said side wall portion includes a plurality of generally coaxially arranged cylindrical portions disposed in radially spaced apart and at least partially axially telescoped relation.
 16. The apparatus of claim 15 wherein, said inner end portion of said condenser means includes a plate affixed across the inner end of said side wall portion. 